(1) Field of the Invention
The present invention relates to a process for producing a monochloroacetaldehyie (hereinafter referred to as MCA) alkoxycarbonylhydrazone.
The hydrazone derivative obtained in the present invention is useful as an intermediate for drugs, agricultural chemicals, etc.
(2) Description of the Prior Art
MCA alkoxycarbonylhydrazones are compounds known as intermediates for drugs, agricultural chemicals, etc. Various processes are known for the production of said compounds. For example, Japanese Patent Application Kokai (Laid-Open) No. 23974/1978 discloses a reaction of a halogenoacetaldehyde or an acetal form thereof with a lower alkyl carbazate in an aqueous medium. The reaction is carried out in a strongly acidic state of pH 1 or lower. As an improved process therefor, Japanese Patent Application Kokai (Laid-Open) No. 31649/1982 discloses conducting the above reaction with the pH of the reaction system being maintained at 3.5-5. All of these reactions are carried out in an aqueous medium because MCA is very unstable and quite easily polymerizable. In addition, MCA cannot be stored stably over a long period of time and accordingly, must be stored in an aqueous solution The transfer of the MCA dissolved in the aqueous solution into an organic layer is also very difficult. Generally, MCA is produced by chlorination of paraldehyde, acetaldehyde or vinyl acetate and immediately stored in an aqueous solution. The thus produced MCA, however, inevitably contains impurities such as dichloroacetaldehye and crotonaldehyde. Therefore, the hydrazone derivative produced according to the process disclosed in Japanese Patent Application Kokai (Laid-Open) No. 31649/1982 has a purity of about 95% at best. Thus, aqueous solutions of MCA produced by chlorination of paraldehyde, acetaldehyde, vinyl acetate or the like are not preferable as a starting material for producing a hydrazone derivative of high purity.
As mentioned above, MCA as a starting material for producing MCA hydrazone derivative is stored in approximately 40% aqueous solutions that contain impurities. Therefore, the reaction of MCA must be carried out in an aqueous medium. As a result, the hydrazone derivative crystals precipitated in the reaction contain water and are in the form of a very viscous lump, making the washing operation inefficient. It is difficult to separate the water and purify the crystals. Moreover, the hydrazone derivative obtained has a purity of 95% at best and a yield of 50-90%.